X-ray Target Assembly with Segmented Vacuum Envelopes
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Solution Overview
Problem
X-ray target assemblies in linear accelerators face limited longevity due to oxidation at elevated temperatures, with conventional solutions either complicating vacuum designs or limiting dose-rate output through reduced electron beam power or using low-strength oxidation-resistant materials.
Innovation Solution
The X-ray target assembly features a substrate with a target enclosed in a volume substantially free of oxygen, evacuated or filled with inert gas, and optionally a second volume under the target with a hydrogen or inert gas environment, using materials transparent to electrons and X-rays to prevent oxidation and extend target life.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the target is placed within the vacuum envelope, then oxidation protection is improved, but device complexity increases due to added vacuum walls and interface considerations
Solution Approach 1:
The invention divides the vacuum system into two separate envelopes: the accelerator vacuum envelope and a separate target chamber vacuum envelope. This segmentation allows the target to be protected from oxidation in its own vacuum environment without complicating the main accelerator vacuum design, as the two vacuum systems are independent and can be maintained separately.
Solution Approach 2:
The invention introduces an intermediary transfer chamber that connects the accelerator vacuum envelope to the target chamber vacuum envelope. This intermediary allows electron beams to pass between the two vacuum environments while maintaining vacuum integrity in both systems, enabling target protection without requiring the entire accelerator to be in vacuum.
2Duration of action of stationary object
If the electron beam power is reduced, then target heating is reduced and target life is extended, but dose-rate output is limited
Solution Approach 1:
The invention creates an inert vacuum environment around the target using a separate vacuum envelope. This protects the target from oxidation even at high temperatures, allowing the electron beam power to be maintained at high levels for maximum dose-rate output without compromising target life through oxidative degradation.
3Duration of action of stationary object
If oxidation resistant materials such as gold or platinum are used, then target longevity is improved, but material strength is reduced and beam power is limited
Solution Approach 1:
The invention uses a vacuum environment as the protective medium instead of relying on oxidation-resistant materials. This allows the use of high-strength materials like tungsten or copper for the target, which can withstand high beam powers and mechanical stresses while the vacuum prevents oxidation, thus maintaining both longevity and strength.
Solution Approach 2:
The invention employs composite construction where a high-strength material (such as tungsten or copper) serves as the target substrate, and this substrate is protected from oxidation by the vacuum environment. This composite approach of material selection combined with environmental protection achieves both high strength and oxidation resistance.
4Duration of action of stationary object
If the target assembly is moved during exposure, then volumetric power deposition is reduced and target life is extended, but device complexity and operational difficulty increase
Solution Approach 1:
The invention uses the vacuum environment to protect the target from oxidation, eliminating the need to move the target during exposure. The target can remain stationary while the electron beam is directed at it, simplifying operation while the vacuum prevents oxidative damage that would otherwise require target movement to extend target life.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This solution effectively prevents catastrophic oxidation, allowing for higher dose-rate output and extended target life by isolating the target from oxygen, either within or outside the vacuum envelope, while maintaining efficient electron and X-ray production.
Implementation Method 1
incident electron beams strike a target to generate X-rays
Implementation Method 2
The volume is evacuated to remove oxygen
Data Source
Figure 1
Figure 2A~2C
Figure 3A~4
AI summary
An X-ray target assembly includes a substrate, a target supported by the substrate adapted to generate X-rays when impinged by an electron beam, and an enclosure over the target providing a volume for the target. The enclosure is made of a material substantially transparent to electrons. The volume is substantially vacuum or filled with an inert gas.